Guest Stars William B. Davis as Cigarette-Smoking Man Annabeth Gish as Special Agent Monica Reyes Chris Owens as Special Agent Jeffrey Spender Lauren Ambrose as Agent Einstein Robbie Amell as Agent Miller Barbara Hershey as Erika Price Alan C. Peterson as Mr. Y Anjali Jay as Dr. Joyet Co Starring Sandy Da Costa as Alien Jeremy Schuetze as Young CSM Fiona Vroom as Young Cassandra Naiah Cummins as Nurse Erica Govier as Young Erica Harry Han as Male Paramedic Jett Klyne as Young Spender Arggy Jenati as Female Paramedic Alexandre Campion as Young Mr. Y Uncredited Mike Dopud as Mr. Y's Henchman